Active blend

[Smilodon]

In my latest project I'm using two EMG 40HZ pickups. Originally they were wired up to blend, volume and tone pots (And a mode switch, but that's irrelevant)

The pickups sound great, but I have problems with insertion loss. (Both volumes on max make the signal weaker) I tried using two volume pots instead of volume and blend, bit it's not much better.

It looks like an active blend pot is the only way forward. EMG have what I want (EMG ABC), but I'm not able to find one in Norway, or someone that sell Internationally (Apparently EMG limits export in their agreement with dealers ).

So, does anyone know of a similar product that is easier to source?

I'm hoping to avoid building preamps for the pickups...

edit: I could also use EMG "BTS Control" or "BTC Control" but have to be sure that it's the version made for passive pickups.)

 

[SGD Lutherie]

It's not really "insertion loss", because noting is being inserted in the signal path. That term applies to things like passive tone stacks, which need a gain recovery amp.

What's going on is impedance loading. One pickup loads down the other. Another more subtle thing going on is phase cancelation/reinforcement. Some frequencies will be notched with two pickups on, while other might be boosted. You often lose mids.

An active blend will help with the impedance loading. But I'm surprised that you are getting a weaker signal in the first place. Doesn't happen on any of my basses, but then I'm not using EMG HZs. There is a tonal difference though. which is why I rarely use both pickups on full.

 

[Smilodon]

Sorry. You are right. It's impedance loading.

And I just checked now. There isn't a huge drop in volume at max but a drop in mid frequencies, it just sounded like a volume drop because the EQ was set mid heavy.

 

[Derek Balonek]

Do these are passive pups? How's the blend wired? Is it the "no-load" (IIRC walterw called it that) or standard? No-load is similar to standard wiring but the wire to ground is omitted. A 500k m/n pot works best for this.

 

[Smilodon]

Yes, they are passive pickups.

The blend isn't wired at the moment. I'm using two volumes until I can figure this out.


No load pots doesn't really work very well for volume AFAIK. They were originally intended for use with tone control. Volume controls work as voltage dividers, so if the ground is omitted the volume control wouldn't work at all.

The only "special" thing about the wiring in my bass is that the pickup output is wired to the wiper of the pot. This is done to prevent muting of both pickups if one is muted. It should otherwise work exactly the same as the "traditional" way.